The field of the invention relates generally to electrical power devices, and, more particularly, to a dynamoelectric machine including a main lead insulator and associated methods.
A dynamoelectric machine, such as an electrical power generator, typically includes a stator and a rotor, each having respective windings. The rotor is mounted to a rotatable shaft that is typically driven by steam or combustion. As the shaft rotates, the rotor turns within the stator to generate electrical power.
A pair of axial leads may extend axially in axial passageways within the shaft, each of the pair of axial leads connecting to respective radial leads extending through respective radial passageways opening outwardly from the shaft. The radial leads, in turn, may each connect to respective main leads that extend axially within respective main lead receiving recesses formed in the surface of the shaft. Each main lead connects to a set of windings on the rotor. The connected main, radial, and axial leads supply an excitation current from an exciter, also typically driven by the shaft, to the rotor windings to thereby produce the magnetic flux necessary for generating electrical power as the rotor turns within the stator.
In an electric power generator, for example, the shaft and rotor spin at considerable speeds during operation of the generator. Thus components like the windings and main leads are subject to significant centrifugal forces. The main leads may also be subject to axial forces as well. There is also considerable heat generated as a result of electrical current flowing through the windings of the rotor and stator that may lead to unequal thermal expansions of the components. It may be desirable, therefore, to pack the space between a main lead and the main lead receiving recess in which it extends so that the lead remains relatively well secured and insulated within the recess.
Moreover, to reduce centrifugal loading, newly designed leads are being made lighter, which, in turn has resulted in these leads having smaller cross-sections. This makes effective packing of a main lead within a main lead receiving recess even more difficult. Additionally, in-service lead failure frequently requires extensive shaft machining to remove arc-damaged material from the main lead receiving recess, which results in the main lead receiving recess being made larger. This increases the difficulty in adequately repacking the space between a main lead and the contours of the main lead receiving recess after the in-service failure has been corrected.
Conventionally the space has been filled with laminated mica sheets. Such sheets, however, tend to migrate axially along the shaft as the shaft rotates. The migration can be severe enough to require disassembly and repacking. Efforts have been made to address the problem of stress on the connection between the main lead and rotor windings induced as the shaft rotates. U.S. Pat. No. 6,020,770 to Jones et al., for example, provides a connector support block that is held by the rotor windings of a generator and into which the end of a main lead fits to limit deflection of the main lead near the point of connection to the rotor windings. There remains, however, a need for ways to more effectively pack the main lead and, more especially, to mitigate the axial migration of conventional packing, such as laminated mica sheets.
With the foregoing background in mind, it is therefore an object of the present invention to provide a rotor assembly, for example, having more effective packing of a main lead.
This and other objects, features, and advantages in accordance with the present invention are provided by a rotor assembly including an main lead insulating assembly into which the main lead is packed. More particularly, the rotor assembly may include a shaft that has a main lead receiving recess in the outer surface.
The main lead insulating assembly lines the main lead receiving recess and may include at least one insulating bottom block and at least one insulating sidewall block connected thereto. The at least one insulating bottom block may include at least one projection which is received in at least one corresponding recess in the shaft. The projection thereby restricts axial migration of the at least one insulating bottom block during rotor operation.
The at least one insulating sidewall block may be secured to and extend outwardly from the at least one insulating bottom block, such as with at least one interlocking joint. A main lead may be received in the main lead insulating assembly lining the main lead receiving recess.
The at least one insulating bottom block may be a single insulating block. The at least one insulating sidewall block may comprise a pair of spaced apart sidewall insulating blocks. The at least one insulating bottom block and the at least one insulating sidewall block may each comprise glass-epoxy.
The rotor assembly may further comprise at least one securing wedge also received in the main lead receiving recess radially outward from the main lead. The rotor assembly also may include an axial passageway, and, may further include a radial passageway connected to the axial passageway opening radially outwardly from the shaft. An axial lead may be received in the axial passageway, and a radial lead may be received in the radial passageway. The axial lead may connect to the radial lead, which, in turn, may connect to the main lead.
An additional aspect of the present invention pertains to a method for installing a main lead for a rotor assembly comprising a shaft having a main lead receiving recess in its outer surface and a rotor mounted to the shaft. The method may include lining the main lead receiving recess with a main lead insulating assembly. Lining of the main lead receiving recess may include securing at least one insulating bottom block to the shaft so as to be restricted at least in axial movement. The method may further include securing at least one insulating sidewall block to the at least one insulating bottom block to extend outwardly therefrom. The method additionally may include positioning the main lead in the main lead insulating assembly.